This invention relates to a piston type gauge protector having a safety relief, and the like, for protecting pressure gauges or pressure transducers connected to flow lines.
In general, it is important to protect pressure gauges which are used for monitoring various conditions in high pressure environments, such as high pressure pipelines, gas well tubing, and fracturing and acidizing equipment used in well servicing operations, from the fluids in those environments so that the pressure gauges will remain functional.
By way of example, in pumping a fluid through a pipeline it is necessary to monitor the pressure within the pipeline by means of a pressure gauge. This monitoring is necessary, for example, because the pressure measurements obtained by the monitoring process can be used to determine the extent of erosion of the tubing within a pipeline, which tubing may be that which is used in a gas well. However, because of the delicate nature of pressure gauges used in the monitoring process, precautions need to be taken to protect the pressure gauges. For example, in the previously mentioned gas well tubing a gauge damaging force may result from the large pressure pulses which are generated by fracturing fluid pumps located upstream from the pipeline locations at which the pressure gauges are to be connected to monitor the pipeline pressure. Also it is necessary to protect the pressure gauges from the effects of the fluids in the pipelines themselves to prevent damage to the gauges.
Typical prior art gauge protectors are disclosed in U.S. Pat. Nos. 4,297,891; 4,199,991; 4,192,192; 2,147,031; 2,064,268; 2,618,978; 1,867,779; 1,836,682; and 1,799,832 and Canadian Pat. Nos. 805,945 and 1,069,336. In both such prior art gauge protectors, a resilient bag or diaphragm is used to separate the fluid in the pipeline from that in the gauge. Alternatively, a piston may be used in place of the resilient bag or diaphragm.
However, gauge protectors using resilient bags, diaphragms, or pistons to separate the fluids between the pipelines and gauges will ultimately bottom out in the gauge protector housing giving a false reading on the pressure gauge since the movable member in the gauge protector will no longer respond to increases in pipeline fluid pressure.